Newtec M6100 - 12.11 Basic Interoperable Scrambling System (BISS)

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Features Descriptions M6100 Broadcast Satellite Modulator
12.11 Basic Interoperable Scrambling System (BISS)
12.11.1 Content Scrambling Modes
The BISS application on the M6100 protects the content of a MPTS (multi-program transport
stream) during transmission.
BISS uses a Session Word as a scrambling key. The same key is used to scramble all programs.
The M6100 supports two different encryption modes with different scrambling behavior: standard
mode or raw mode.
12.11.1.1 Standard Mode
The Standard Mode is fully DVB-compliant. In this mode, the payload of all packets is scrambled,
except for the PSI/SI tables (PIDs<0x1F and PMT tables).
The scrambling starts when a valid PAT table is found and all existing PMT tables are identified.
When no PAT is detected within 1 second, the scrambling is however started in raw
mode.
Each PMT table is updated with a proper CA descriptor (Conditional Access descriptor) if the
descriptor is not yet available. The scrambler also inserts a CAT when no CAT is present in the
transport stream.
In case of CRC error on the PAT or PMT, or if the incoming stream appears to be scrambled (CA
descriptor in the incoming PMT), the scrambling is stopped to avoid making the signal
unrecoverable. This behavior can be overruled with the “Scrambling Suppression” parameter.
Scrambling Suppression (for Standard Mode)
When operating in the standard mode, the scrambling by default stops in case of CRC errors on
the PAT or a PMT or if a PMT already contains a CA descriptor. The reason is that the risk to
scramble PMTs, or erase previous scrambling information would make the stream unrecoverable by
an IRD.
It is possible to overrule this behavior, if the protection of the stream is more important than its
decodability in case of errors. Do this by disabling the “Scrambling Suppression” parameter.
Keep this suppression enabled when the TS has high priority and getting the TS to the receiving
end has more priority than scrambling the TS.